64 SYLVICULTURE IN THE TROPICS 



PT. I 



beneficial functions which have not been appreciated 

 yet. 



The vegetable parasites may be broadly divided into 

 fungoid and phanerogamous parasites. On the subject 

 of the former, volumes could be written by specialists, 

 and even had I the requisite knowledge, I have not 

 the space here to go into details. They may be sub- 

 divided into root-fungi and stem- and branch-fungi, 

 and to them may be added saprophytic fungi which 

 live on perishing vegetable matter and do not attack 

 healthy trees. 



The root-fungi attack the roots of trees and they 

 pass from one tree to another often by root contact. 

 Such is, for example, what is called " Spike " in the 

 Sandal tree, which is itself a parasite, and destroys the 

 haustoria, through which the latter obtains nourishment 

 from other plants. An example of Fomes Pappianus 

 destroying large numbers of Acacia arabica in India is 

 cited in the Indian Forester} Here it is presumed 

 that although the spores entered through wounds above 

 ground, the infection from tree to tree has been com- 

 municated by root contact. The " leaf disease " of 

 Ceylon, which destroyed the cotfee plantations, was a 

 fungus (Hemileia vastatrix) which spread from the 

 forests. In the same way, the " Cacao-canker " is also 

 due to a fungus spreading from the forests. Similarly, 

 dry-rot in trees is due to fungoid attacks. As several 

 of these fungi select special species for their attacks, one 

 of the greatest safeguards for the forest against the 

 spread of fungoid diseases from infected centres is to 

 have a mixed forest, i.e. a forest composed of a variety 

 of species. In pure forests the disease, finding congenial 

 hosts on all sides, is much more liable to spread, and 

 energetic measures may have to be taken to prevent 

 damage and perhaps destruction of the crop. Among 

 the remedies may be cited the removal and burning of 

 diseased twigs, branches, or even whole trees, the 

 smoothing and tarring of wounds, the destruction of 



1 E. E. Fernandez in Indian Forester, vol. xxix. No. 6. 



